A parasympatholytic agent is a substance or activity that reduces the activity of the parasympathetic nervous system. (The parasympathetic nervous system is often colloquially described as the "Feed and Breed" or "Rest and Digest" portion of the autonomic nervous system. The parasympathetic nervous system becomes strongly engaged during or after a meal and during times when the body is at rest.)
The term parasympatholytic typically refers to the effect of a drug, although some poisons act to block the parasympathetic nervous system as well. Most drugs with parasympatholytic properties are anticholinergics.
"Parasympatholytic" and sympathomimetic agents have similar but not identical effects. For example, both cause mydriasis, but parasympatholytics reduce accommodation (cycloplegia), whereas sympathomimetics do not.
Parasympatholytic drugs are sometimes used to treat slow heart rhythms (bradycardias or bradydysrhythmias) caused by myocardial infarctions or other pathologies, as well as to treat conditions that cause bronchioles in the lung to constrict, such as asthma. By blocking the parasympathetic nervous system, parasympatholytic drugs can increase heart rate in patients with bradycardic heart rhythms, and open up airways and reduce mucous production in patients suffering from asthma.
- Overview at salisbury.edu
- Parasympatholytics at the US National Library of Medicine Medical Subject Headings (MeSH)
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